Surface Doping to Suppress Iodine Ion Migration for Stable FAPbI₃ Perovskite Quantum Dot Solar Cells

Abstract Formamidine lead iodide (FAPbI₃) quantum dots (QDs) have attracted great attention as a new generation of photovoltaic material due to their long carrier diffusion length, benign ambient stability, and light‐harvesting ability. However, its large surface area with inherent thermodynamic instability and highly defective ionic termination are still major obstacles to fabricating high‐performance devices. Herein, a metallic ion dopant is developed to post‐treat FAPbI₃ QDs immediately after their fabrication by using a metal‐glutamate salt solution. Both experimental and theoretical results show that alkaline (earth) metal ions (Mg²⁺, Na⁺, and K⁺) in their glutamate salt can not only successfully substitute insulating long‐chain ligands to form thinner ligand shells but inhibit the formation of iodine vacancies on the surface of QDs. As a result, the glutamate‐Mg based solar cell exhibits a champion efficiency of 13.48%, and the other two solar cells treated by glutamate alkaline metal salts (Na⁺ and K⁺) achieve photoelectrical conversion efficiencies of 13.26% and 11.88%, respectively, all of which are higher than of control cell with an efficiency of 11.58%. Therefore, this substantial progress provides intuitive cognition and guidance for the improvement of photoelectric performance and the commercial application of quantum dot solar cells.